Cork composition



Patented Mar. 28, 1944.

UNITED STATES PATENT OFFICE 1 061m, COMPOSITION No nil-swine.Application May 1, 1939,

Serial No. 271,202 g 12 Claim.

This invention relates to composition material and particularly tocompositions including substances conducive to i'ungus growth. Theinvention, moreover, relates to by-products of cork distillation and toprocesses of producing the same.

More specifically, the invention relates to a regranulated baked corkcomposition and to a stifi' or rigid, light weight, insulating boardcomprising regranulated baked cork and cellulosic material, forinstance, cellulosic fiber, and having fungus growth and/or fireretardant properties, and to a very light weight board of suchcharacteristics.

The present invention is a continuation-in part for my copendingapplication Serial No. 179,867, filed December 15, 1937, which is adivision of my copending application Eerie! No. 46,742,.flled October25, 1935, now patent. No. 2,156,309.

The present light weight insulation board materials comprise, on the onehand, the well known baked corkboard insulation, and on the other, thecellulosic fiber board. These products have disadvantages andlimitations which confine their use to certain fields. For example,present day baked corkboard consisting of 100% cork, is limited in itsfield of application, by high cost, low strength, and small practicalsize of board, which make its use prohibitive for prefabricated wallpanels. It would be impractical to make a board of sufficient size, forinstance, 4' x 10' x 2" of baked oorkboard material. The fiber board hasthe disadvantage of higher weight or density, which means higherconductivity. For

- instance, the weight of a panel or fiber board of the size-hereinabovementioned, surfaced with a high density cement-asbestos board on bothsurfaces, would be about 257 pounds. such makes manual handlingdifilcult and cumbersome. More particularly. fiber board is suscepti-'ble, among other things, to fungus growth. decay. attack-by termites,high moisture absorption. and combustibility. It will be readilyrecognised that the problems of mold growth, termite attack. andexcessive moisture penetration, on a core of fiber board materialencased as above described. but with edges likely to be more or lessexposed, may be serious. In addition, there is. of

, course, the high fire hazard resulting from the use of a combustibleinsulating core. In spite of extensiveresearches aimed at solving someof the problems brought about by theshort-comings of the aforesaidconventional materials, no satisfactory solution, insofar as I am aware,has

been forthcoming. At best, it has been suggested to chemically treatfiber board by the addition 01 arsenic compounds, chlorinatednaphthalene, etc., to make the board resistantto' mold growth 5 andtermite attack, but there are objections to such methods arising out o!the toxic nature of the agents used, and the additionalcosts andprocessing incurred by their use.

The present invention aims to overcome the problems or high density andmold growth, and by a simultaneous treatment: and to provide material01' higher fire resistant character. Moreover, the invention aims toovercome problems of mold growth in present day fiber board is by atreatment that is wholly unobjectionable and not costly. An object ofthe invention is to provide a low, density composition comprising a corksubstance obtained as a residue of a baking treatment which partiallyremoves volatile organic material which is inherent in the cork or isformed during the baking treatment. This cork substance is included withmaterials designated herein by the phrases "regranulated baked cork or,for brevity, "regranulated cork.

Another object of the invention is to provide a compressed compositionof substantially uniform physical character comprising particles ofregranulated cork and a fibrous material obtained .by finely beating thefiber in an aqueous solution of at least 90% dilution to the form ofindividualized fibers of an average length less than about.0.08 inch,and to a non-settling volume density (dry weight) of less than about onepound per cubic foot: the said particles and fiber being insubstantially uniform'volumetric distribution and the said fiber lyingin substantially all directions and presenting with the cork particles,a bonded composition substantially free of parallel matting of the fiberinto planes of cleavage characteristic of cardboard, the fiber .ar-

rangement also being such that there results in the composition a'substantially microcellular structure comprising a multiplicity ofsubstantially uniformly distributed and substantially microscopic voidsconstituting at least 40% 01' the volume of the composition. I Anotherobject of the invention is to provide a low density product comprisingresranulated cork or the like material and organic material, the saidproduct being resistant to fungus growth and to fire.

Another object 01' the invention is to provide to afungus growthinhibiting addition for compositions containinga fungus growth inducivesubstance. I

Afli

granulated cork and cellulosic material, for instance, cellulosic fiber.

Another object of the invention a fungus growth resisting treatment fororganic material, comprising the addition to said material of awater-soluble aqueous distillate of cork.

is to provide Y her object of the invention is to provide a light weightcomposition comprising re- A still further object is to provide a verylight in part be understood and in part be more specifically pointed outin the following description ..-when taken in conjunction with theclaims.

I have discovered that the aforesaid limitations of baked corkboard maybe substantially overcome by producing a am from a compositioncomprising a material which is'now a waste product or the cork industry,that is, particles of regranulated cork or the like, and in particular,by a low density composition. comprising such material and a medium ofextension made in accordance with the procedure of my copendingapplication Serial No. 46,742, now Patent.

No. 2,156,309, and with or without the use of any so called bindersubstance or with the use of such a small percentage of the same as tomake its presence entirely unobjectionable from the standpoint ofincrease in density, increasein thermal conductivity. and even increasein cost. The aforesaid waste product (finely ground regranulated cork)has a density of about six pounds per cubic foot, which is aboutone-half of that of natural cork wood in a similar form. The wasteproduct cannot be used again in the manufacture of baked corkboard.

I may prepare, in accordance with the teachings of my Patent No.2,156,309, an aqueous disperslon of finely divided regranulated cork,better less than about 10 mesh in size, andpreferably between 50 to 200mesh in size, and-a medium of extension and filter aid, for instance, afinely pulped fibrous material su'ch as finely pulped newspaper or woodpulp in th form of individualized fibers that will provide an abnormallylarge non-settling volume of precipitated substance, and subject such aslurry 1 to filtration and a desired pressure to form a matrix of largevolume, which, when dry, has the regranulated cork particles insubstantially uniform volumetric distribution with the fibers lying insubstantially all directions and presentin with the regranulated corkparticles. a continuous bonded com.- position substantially free ofparallel matting of the fiber into planes of cleavage so as to produce asubstantially uniform physical structure that is microcellular andpossesses a multiplicity of substantially microscopic voids havingsubstantially uniform volumetric distribution,-. and constituting atleast about 40% of the volume .of the composition. The uniformity of thestructure will be readily recognized when a section of the matrix is cutlongitudinallyor eitherway 'transversely thereof. All will have asubstan- 'tially similar appearance and will be substantially freeofcleavage planes.- The average individual fiber of the finely pulpedfiber aforesaid-should be'less than approximately 0.08"

'in length and should be sufflciently beaten to giv an abnormally largenon-settling volume of fiber, having, for instance, a density less thanabout one pound per cubic foot, dry weight. In this condition, the fiberwill be somewhat gelatinized. In'the pulping operations, it is desirableto avoid the obtaining of large amounts of colloidal fiber, as such isdetrimental to filtration. Other particulate substances, for instance,those described in my Patent No. 2,156,309, may be used in conjunctionwith the regranulated cork particles. are of a character that would, inthemselves. induce fungus growth, an additional advantage, as willhereinafter be pointed out, is obtained by the use or regranulated cork.Moreover, it will be understood that other fibrous substances, forinstance, those disclosed in said copending application, may likewise beused in place of or in conjunction with the fibrous materials notedabove. Preferably, however, the fibrous'material will be, at least inpart, of acellulosic character to aid in filtration. It will beunderstood, or course, that the percentages of fiber and regranulatedcork or additivematerials'to be used, will be determined in accordancewith the formulae given in my copending application, with adequatecorrection for the inherent cellular structure of regranulated cork.Moreover, suitable binding agents such as, for example, a latex.

or aqueous resinous dispersion, may be utilized'with variations intheamount, dependent upon the structure desired. Also, where it isdesired to obtain the novel waterproofing properties set forth in mycopending application, I may incorporate a small percentage of dispersed.Wax or any of theother waterproofing emulsions set forth in mycopending application Serial, No. 201,082, now Patent No. 2,232,977,whereby capillary action in the finished product will be entirelyeliminated and the. product will be rendered internally waterproof. I

I have further discovered that the aforesaid limitations of fiber boardmaterial may likewise be greatly reduced by the addition of a materialsuch as regranulated cork. By the addition of such material to thecomposition of fi-ber board, definite fungus growth resistant propertiesare obtainable without excessive cost and without introducingobjectionable chemical agents. Moreover, this property is obtained whilesimultaneously decreasing the density of the fiber board product,decreasing its coefiicient of thermal conductivity, markedly improvingits resistance to 'fire hazard, and decreasingits vulnerability tomoisture absorption. 1 have found that the use of 30% or more of thismaterial is desirable to obtain best results. However, it will beunderstood that substantial benefits may be obtained by the utilizationof lesser amounts of such material, but in that case the properties ofthe black in color, lighter in weight than natural fiber board productwill not be as effective from the standpoint of fungus growth.

In speaking ofregr'anulated cork, I desire to emphasize that thismaterial, obtained by baking natural cork, is entirely different bothchemically and physically from natural cork; it is dark or cork, andpossesses expanded cell having certain constituents of the cell wallmaterial re- Where such additive particles moved by volstilisation andothers decomposed by the heat of the baking operation. This chemicaldifference is markedly illustrated by the fact that natural cork, whenadded, for instance, to cellulosic fiber. does not provide fungus growthresistance, but that the regranulated cork material, if properlyhandled, does provide this property. 7

It has been found that th regranulated cork material now obtainable as aby-product of the cork industry, varies somewhat in character. Theweight, color, and chemical characteristics vary due to the methods ofhandling and variations in the baking of the corkboard from which it isobtained as a trimming. These differences cause variations in theresults when regranulated cork is used in the making of a cellulosicfiber insulatural cork usually in the form of broken pieces, butpreferably in the form. of granules, is subiected to a long, thoroughbaking distillation of high temperature, for instance, 400 F. to 800'I". On the other hand, if light weight is the'chief consideration anddistillation by-products are not ill and with only sufficient subsequentpulping or that if the regranulated 'cork be added to the beater priorto pulping the fiber, the fungus growth resistance of the resultingproduct will be adversely affected, and in extreme cases, whereexceedingly large quantities of water areused, may be almost completelyneutralized. This is believed to be due to the extraction of the eifec-'tive ingredient by the hot water. Preferably, the regranulated corkshould be finely ground in order to obtain good distribution of thematerial and intimate contact of the cork with all the fiber. It is alsofound desirable to avoid comparatively strong alkaline agents, such asammonia, and also organiclagents such as latex, which adversely affectthe fungus growth resistance of the resultant product.

Inasmuch as the available regranluated cork is now a waste product ofthe cork industry, is definitely a limiting factor, so far as commercialproduction of the products of the present invention are concerned. Anewsource of regranulated cork or the like is therefore necessary for largeoperations. I have discovered that a prodnot more uniform and moreeffective than the present waste regranulated cork product, maybeobtained by suitable treatment of natural cork materials, and inaddition, that valuable by-product may also be obtained. Moreover, Ihave been able to isolate the substance which is principally responsiblefor the fungus growth resisting properties and by my novel process oftreating the natural cork, I may obtain substantial quantities of thissubstance for use as a treatment unto itself. Moreover, by a modifiedprocess I may obtain resultant cork material that has a density as muchas 50% less than that of the present waste regranulated cork wastematerial of the corkboard industry. Thus, it is a feature of myinvention to subject natural cork material, for instance, shavings orgranules from the cork stopper industry. to a proper type of heattreatment to obta n the foregoing results. The exact nature of the heattreatment will depend upon the dominant characteristic desired in thefinished product.. When fungus growth resistance is the chiefconsideration, and it is additionally desired to obtain distillationby-products as well, the natdesired. the natural cork is heated to about400 F. or more underconditions allowingv a maximum expansion of the corkcells in the shortest possible time and with only a small amount of decomposition and loss of volatile matter.

In the first instance, I have discovered that as much as 45% of volatileby-products may be distilled off and still have a residue suitable formaking the product of the present invention,

that is, the regranulated cork will be of extremely low density, lessthan six pounds per cubic foot: and as low as three pounds per cubicfoot, dependent upon the quantity of by-product distilled. Moreover,where the distillate does not exceed the'above amounts, the regranulatedcork residue will retain sufficient fungus growth resistant substance tomake it completely effective in combating fungus growth of the finishedproduct. of which it is a part. products, about 15% consists of oils andabout 30% consists of an aqueous distillate. The latter may befractionated in the conventional manner and about 5% thereof separated,having a boiling point range of about 45 C. to about 96 C.. and aspecific gravity of about 0.876 to about 0.920. This portion is believedto contain cyclic alcohols and derivatives which make xcellent solvents.The remaining aqueous portion has an acid reaction, a yellowdiscoloration increasing by absorption of oxygen from the air, and aslightly acetic odor, also increasing with oxidation. The water solubleconstituents contained herein are believed to include di-hydroxy andtri-r hydroxy phenols and derivatives and decomposition productsthereof. I have found that this aqueous portion of distillate formedduring the distillation by a decomposition that progresses inwardly fromthe surface of each particle of the cork material during heat treatment,and some of which decomposition material is retained in the bakedmaterial after the distillation or baking is completed, definitelycontributes toward the fungus growth resistant properties of theregranulated cork. This beingthe case, the aqueous portion of thedistillate that is driven ofl in treatment may, therefore, be added tothe pulp suspension in making the products of the present invention withincreased benefits in fungus growth resistance. Moreover, theaqueous-portion of the distillate may be used alone as a treatment forvarious materials, particularly organic substances that are conducive tofungus growth to rovide these materials with resistance to such action.It will. of course, be understood that the amount of distillate to beused will depend upon the conditions of each application. Where this'dstillate is utilized, together with the novel wate" proofing emulsionsheretofore mentioned, it is desirable that the aqueous portion of thepulp suspension have a pH value not lower than 6.0 in order not toadversely affect the flocculating characteristics of the particles ofsaid emulsions.

The oil layer or distillate obtained as above, may be d stilled intovarious fractions having boiling points ranging from 50 C. to 375 C. andspecific gravities from 0.763 to 0.940. I have found that a solidresidue remains above 375 C. These oils are all insoluble in' water andonly 01 this 45% of bycent with relatively little decomposition.

' might otherwise have some appreciable value.

I have, however, discovered that by boiling this distillate with astrong caustic solution and separating a portion of the oil, which issoluble therein, and then redistilling several times, that very clear,almost water white fractions are obtainable that do not discolor onstanding. I

have not been able to determine as yet the chemical nature of theseoils, but they will be readily recognizable from the propertieshereinabove given. Moreover, having now removed the objections to. thisdistillate, a number of uses now suggest themselves. For instance, thesewater white fractions may be used as solvents,

, plasticizers, lubricants, etc.

From the description of this distilling procedure of natural cork, itwill be observed that the high yields of by-products of value obtainablein the operation of producingthe regranulated cork from natural corkwaste is not only exceedingly important from the standpoint ofuniformity of resultant products, but is likewise a procedure likely tobe extremely profitable commercially and to makethe cost of the corkresidue extremely low. It is desiredto emphasize, at this point, thatthe chemical nature and amounts of by-products obtained by the aforesaidbaking and distillation procedure are not to be confused with" thedestructive distillations of the various kinds of woods or bark whereinmethyl, alcohol, acetic acid, acetone and creosote, and in some cases,turpentine and rosin, are the chief products, for the chemical natureand amounts of by-products obtained by the described procedure and theuse of cork therein, are entirely different from the results obtained inany of these known destructive distillations. l

A further feature and one that contrasts with the above method ofhandling the natural cork waste for maximum yield of by-products with asatisfactory regranulated residue, resides in the second methodmentioned above involving the rapid expansion of the cork cells to thelimit, with only a minor amount of decomposition and volatilization. Inaccordance with this procedure, natural cork granules that are not toolarge in size (about A") are brought under proper conditions, forinstance, in a rotary kiln, into quick and intimate contact with aheating agent, such as superheated steam of about 400 F. to 500 F. Bythis procedure, the cork cells of the granules may be expanded severalhundred per-' The cork granules, after being expanded, are cooledwithout there being any pressure thereon, so

that the maximum volume is obtained. Subsequently the regranulated corkthus obtained is finely ground in the same manner as the residueobtained by the above distillation method. The regranulated corkobtained in this manner will have suflicient internal decomposition toprovide eflectiveness in resisting fungus growth, 1. e., the surfaceportion of the natural cork material, which normally prevents its use asa fungus growth resistant product, is decomposed in the process to makeit effective. Moreover, a maximum lightness of cork product is obtainedin this manner. Thus, whereas the regranulated cork now available as awaste product of the cork industry and referred to above, has a. densityof about six pounds per cubic foot, the regranulated cork of similarsize made by the present procedure of expanding the cork to the limit,as herein described, may have a density even as low as three pounds percubic foot: in other words, about one-half the density of the pressently available material. It will, therefore, be recognized thatregranulated cork made in accordance with my invention can be made to gotwice as far by volume and produce a product that is about lower inweight when about 60% of regranulated cork is used in the composition,as against using present regranulated cork.

I have further discovered that the fire resistance of compositionproducts made with the regranulated cork material is' definitelyimproved; for instance, regranulated cork'will greatly enhence the fireresistance of cellulosic fiber insulating board when added to thecomposition of such a product. Theamount of this improvement will dependupon the size, amount, and character of the fiber, which determines, tosome extent, the size and character of the voids in the finishedproduct. Small, finely divided fiber and fire resistance. Moreover, Ihave found that the addition of bentonite, together with theregranulated cork addition, produces results, for instance, in thecomposition of cellulosic insulating fiber board that is out of allproportion to expectations so far as improving fire resistance goes.Moreover, bentonite may be added to such composition to secure theseremarkable results without adversely affecting the moisture absorptionof the finishedproduct. This is also true when added water-repellentsubstances, for instance, those of my copending application Serial No.201,082, now Patent No. 2,232,977, are present, but in such instancesthe pH value of the suspension is preferably near 7 for optimum moistureresistance. The bentonite also increases the strength of the finishedproduct. Accordingly, it is a further feature of the invention to makeproducts of a composition, preferably one prepared in accordance withthe steps of my copending application, which composition contains finelydivided cellulosic fiber, regranulated cork, and bentonite. Thecomposition may also include some finely. divided asbestos fiber and asmall amount of alum may be added to improve filtration and make thecomposition neutral. Moreover, a small amount of dispersed paraffin ofthe character described in my copending application Serial No. 201,082,now Patent No. 2,232,977, may be added to obtain further waterproofingqualities." A product made from a large volume .suspension of such acomposition in value, and may be made at low cost. It will be recognizedthat such a combination of properties make an ideal insulating board orcomposition which the art, insofar as I am aware, has never before beenable to achieve in practice.

In connection with the use of the regranulated cork made by theexpansion process herein des,s4s, 4s1 scribed, I desire to point outthat the general formula set forth in my copending application SerialNo. 46,742, new Patent No. 2,158,309, to

' to that described in said copending application, I have found itdesirable to use about 43% of the new, regranulated cork of about threepounds density instead of .using about 65% of the present regranulatedcork waste of the cork industry of six pounds density. In other words.the percentage of fiber is still further increased. These amounts giveapproximately the same volumetrlc composition which determines thestructure.

For the purpose of "giving those skilled in the art a betterunderstanding of the invention, the following illustrative examples aregiven.

Example No. 1

To about 1000 pounds of a latex dispersion, about 20 pounds ofnewspaperare added and subjected to high speed mechanical disintegrationuntil the average individual fiber is about or less than approximately0.08- inch in length. To this medium of extension, about 40 pounds offinely ground regranulated cork (trimming of baked cork board) are addedwith high speed mixing. The mixture is run into molds which in theirsimplest form are rectangular boxes, the bottoms of which are filterscreens of approximately 16 mesh. It is essential to fill the formquickly and agitatethe mixture while still very dilute so as to obtain auniform suspension in the mold and, once the matrix is formed, it mustnot be disturbed by further mixing. This latter point is importantbecause in filling a form with a dilute aqueous mixture, as used herein,to the depth required, a considerable washing effect is encountered,tending to disturb and wash out the matrix which is formed immediatelyadjacent to the filter screen during the filling process. If such localwashing out is allowed to occur during filling, the slabs will haveholes and regions of decreased thickness when finished, eventhough themolds are apparently absolutely evenly filled at the end of the fillingoperation. By noting the above precaution, an even and uniform slab canbe made.

After the major portion of the liquid has filtered off, a cover made of16 mesh screen and fitting accurately inside the mold,- is placed on thematerial and a slight pressure is applied. It has been found that apressure as little as about2 to about 4 pounds per square inch issufficient to produce the result required in this present case. Thepressed slabs will still contain 400% to 600% aqueous liquid calculatedon the dry weight of the material used. The slabs are then removed fromthe forms by inverting them onto another screen and are placed in adryer. The filtrate is, of course, recovered and used for subsequentbatches. The dried material will have a density of approximately 7 to 9pounds arge non-settling per cubic foot, which is lower than corkboarditself and a thermal conductivity-of approximately 0.24. Those skilledin the art will readily understand how unit operations of the above typemay be conducted on a continuous scale. 7 In the above illustration, itis advisable to have the cork as finely powdered as practicable,certainly less than about ten mesh and preferably about 50 to about 200mesh. This'ls contrary to prior methods of corkboard manufacture whereinlarge granules are used. The use of an extension medium as hereindescribed in the manufacture of a oorkboard is a novel feature of theprocess. The establishment of a critical range of composition, namely,about 20 to about 50% medium of extension, with the optimum valueestablished at about 25%, is an important factor of control. Theformation of a greatly extended matrix under filtration and its gradualcompression without interrupting its continuous physical structure, isanother important principle of the invention.

' Example No. 2

The same general procedure as described in connection with Example No.'1 is followed. The materials used are about 1000 pounds of 15% latexdispersion, about pounds of a medium of extension (dry weight), andabout 60 pounds of finely powdered exterior bark portion of corkboard.The boards are'made still thinner, about A; of an inch for, say, soleleather substitute or flooring material, and a still higher compressionis used, sufficient to reduce the aqueous content to about to A strong,flexible, physically uniform structured material having a fine texture,free from visible voids, or cork granules, or visiblefiber, is obtained.For certain purposes, hardening agents, such as sodium silicate, variousresins, etc., may be added. Of course, in using latex, it may becompounded according to well known principles with the use ofanti-oxidants, accelerators, etc.

I have found that the addition of a small percentage of dispersed wax tothe medium of extension will entirely eliminate any capillary action inthe finished product and will render it internally waterproof. For manyproducts, this is extremely important. I have found that this war: maybe satisfactorily incorporated by slowly Example No. 3

100 pounds of cork waste as obtained from the cork stopper industry areground to about /4. mesh and less and placed in an iron retort andheated by direct fire so that the inside temperature will be about 400F. to 600 F. The heating is continued until about 45 pounds ofdistillate are collected. The retort is then cooled and the mass ofbaked cork is finely ground. The distillate is allowed to settle and thewater layer (about 30 pounds) drawn off from the bottom. This is thensubjected to fractional distillation by means of which 1% pounds" ofalmost colorless distillate boiling between 45 C. and 96 C. areseparated. This will be referred to as distillate AA. The remainder ofthe aqueous portion, about 28 pounds is put aside for use in theinsulating board and this will be referred to as distillate .1113. Tothe oil layer, of about 15 pounds, about 40 pounds of 20% caustic sodasolution is added and distilled until about 20 pounds of distillate arecollected which will contain an oil layerof about three pounds. This oillayer is distilled several times and a clear, almost waterwhitedistillate is obtained which will be called distillate A (boiling pointrange 68 C. to 220 0., density range 0.77.6 to 0.860) The two layersremaining in the flask are separated by drawing of! the aqueous causticlayer from the oil layer. The latter is distilled several times andabout 7 pounds of a clear oil varying in color from almost water-whiteto a pale greenish yellow are obtained. Thisdlstillate, which will bereferred to as distillate OB, has a boiling point range from 245 C. to345 C. and a density range from 0.860

to 0.866. The aqueous caustic layer is neutral-' ized with HCl and theoil layer that is precipitated is separated and distilled several timeswhereby about pounds of a pale reddish golden oil is obtained having aboiling point range of 210 C. to 235 C. and a density range of 1.022 toLOIS-called distillate 00.

From the above operations there are obtained four refined distillatesAA, 0A, OB, and 0C which do not readily discolor on standing, and whichmay be found useful for the several purposes suggested above and wouldbe sold as Toy-products in carrying out the invention commercially. Thedistillate AB and the ground regranulated cork are used as follows.

To about.3,000 pounds of water, 63 pounds of newspaper stock are addedin a beater and the fiber suspension is pulped while steam is added toheat the water. When the fiber has been sufficiently pulped to obtain alarge non-settling volume of the order of about one-pound per cubic footas described in my co-pending applications aforesaid, the pulpsuspension is run into a storage vat and allowed to cool. In practiceother batches are made while the cooling takes place. While mixing bymeans of a high speed mixer installed in the vat, about 20 pounds of a50% paraffin emulsion such as described in my copending application Ser.No. 271,201 is added. After this addition the 55 pounds of regranulatedcork prepared above and the distillate marked AB are added and mixedonly long enough to obtain an intimate uniform dispersion whereupon themixture is immediately, run into molds, de-

watered, and dried as described in the above pending application. Incommercial practice the filtrate is recovered and used over again sothat any extracted water-soluble matter is retained in the system. Thedried board thus produced will be found to have a density of only about5 to 7 pounds per cubic foot.

If a piece of this material is placed in a jar with some water to supplymoisture and is inocculated with the common green or black mold and Ithe jar is covered and kept at a temperature of about 80 F., there willbe no mold growth after two weeks time. In fact the seed mold graduallydies off. 1

The thermal conductivity of this board will be found to be only about0.27 B. t. u. etc. at a mean temperature of about F. The moistureabsorption will be only'about 5% after a 72 hour immersion. The boardhas no capillarity. The fire resistance will be such as to make theboard very slow burning under the standard test.

Example No. 4

125 pounds of natural cork waste as used in Example No. 3 are ground tomesh and less and fed into a horizontal, rotating cylinder andsuper-heated steam at a temperature of about 475 F. is passedtherethrough while rotating the cylinder. After, about 20 minutes theexpanded tained.

About-68 pounds of newspaper stock and 32 pounds of asbestos are pulpedin about 3,000 pounds of water as in the above example. To the cooledsuspension about one pound of- 50% paraffin emulsion of the same kind asused above is added with high speed mixing. Eighty pounds of bentoniteare then added and this is followed by about 19% pounds of alum which issufiicient to give a neutral color reaction with brom-thymolblue. Afterthis, the 100 pounds of regranulated cork prepared above are added andthe mixing continued only long enough to get an intimate anduniformdispersion after which thesuspension is immediately dewatered inmolds and dried in the same manner as in Example mold growth resistantwhen tested as above.

The conductivity will be only about 0.31 B. t. u., etc., at a meantemperature of 60 F. and the moisture absorption will be only about 14%after a 72 hour immersion. The rupture modulus will be over, 100 poundsper square inch.

Even though the board contains over 50% combustible matter, it will ,befound extremely fire resistant. When placed over the hottest part of aBunsen burner for half an hour, a oneinch thick board will show hardlymore than a white discoloration where the flame strikes it. Hardly anysmoke is given off at all, and no discoloration due to any combustioncan be seen on the top of the board. The board does not burn away wherethe flame strikes it even though it gets red hot. There is no sparking.Such a board has sufiicient fireresistance to be put to any buildingconstruction purpose.

Example No. 5

In the commercial production of fiberboard, cane or wood fiber isdigested and pulped to produce a pulp suspension. About 10% to 20% ofnews stock which has been disintegrated in an engine heater is added. Tothis cooled pulp suspension, about of parafiin emulsion of the type usedabove is added. Then about 30% to 60% of commercial regranulated corksuch as is.

now obtained from the cork industry, is added, and as soon as anintimate mixture is obtained it is fed into an Oliver board formingmachine where it is dewatered and formed into a continuous board whichpasses through a continuous dryer. The filtrate from the Oliver isreturned to the beater and used over again, forming a closed system sothat any water soluble extracted Example No. 6

To about 3,000 news stock and pounds of cane fiber stock, are added andpulped in a beater to a uniform suspension. About one pound of parafiinemulsion, such as used above, is added and finally When cooled, theexpanded cork is finely ground. About '100 pounds are obpounds of water,20 "pounds ofabout 450 pounds of aqueous distillate of the kind referredto in Example No. 3 as distillate AB. The pulp suspension isthendewatered and formed into a board having a'moisture content of 67% (200%based on the dry weight of the board) The board is then finally dried.This board will be found to be resistant to mold growth. In commercialpractice, the filtrate is, of course, recovered and used over again insubsequent batches.

From the foregoing description of certainexemplified embodiments of myinvention, it will be readily discernible that I have provided, amongother features, entirely new cork compositions and cork material, newfungus growth retardation and elimination additions for susceptiblecompositions, new fire retardant substances, and methods of treatingnatural cork materials to obtain new cork products and valuableby-products. It will be understood that the principles and features ofmy invention are not limited to the preferred structures, nor to theconventional long fiber board compositions, but may be applied to alltypes of compositions regardless of structure, where one or more of thebenefits of fungus growth resistance, light weight, low thermalconductivity, improved moisture and fire resistance, and low cost aredesirable factors. It will also be apparent that many changes inprocedure and composition may bemade and others will readily suggestthemselves to those skilled in the art, all, however, without departingfrom the spirit and scope of 'my invention, which is to be construed asbroadly as the following gaims taken in conjunction with the prior artmay allow. Moreover, by the present invention, there is no waste corkmaterial since all portions may be used. The terms regranulated cork?and regranulated baked cork unless otherwise qualified herein areintended to be generic to the cork substances disclosed herein and toembrace not only the waste product regranulated .cork of the cork boardindustry, but also the baked natural cork waste and the rapidly expandedcork waste of the present invention, all of which cork substances areobtained as a result of a heat treatment which forms or liberates.fungus-resisting products in the cork but doesnot remove such productsbeyond such limit as leaves the cork sub stance resistant to fungusgrowth. Moreover, the term uniform volumetric distribution as used inthe specification and claims, is intended to mean uniform distributionin three dimensions.

I claim:

2'. A light weight cellulosic fiber insulating material comprisingcellulosic fiber and to 60% of regranulated baked cork, said baked corkhaving the property of' resisting fungus growth.

3. A light weight insulation material having fire resistant and fungusgrowth retardant properties, comprising organic fiber, regranulated corkhaving the property of resisting fungus growth, asbestos fiber, andbentonite.

4. A light weight cellulosic fiber insulating board having fungus growthresistant properties and having low moisture absorption. comprisingcellulosic fiber, regranulated baked cork having the property ofresisting fungus growth, and dispersed paraffin, said board having adensity less than about twelve pounds per cubic foot and having amoisture absorption of less than'10% by volume in '72 hours waterimmersion.

5. A fungus growth resistant composition adapted for insulationcomprising organic material normally having fungus growth supportingtendencies and an inhibiting agent in sufficient amount to overcome suchtendencies, said inhibiting agent comprising a fungus growth inhibitingregranulated baked cork. I

6. A fungus growth resistant composition adapted for insulationcomprising an organic material normally having fungus growth supportingtendencies and an inhibiting agent in sufiicient 1. A light weightcompressed composition adapted for insulation comprising /2% to 5% ofrubber in the form of latex, finely ground "rcgranulated baked cork"particles having the property of resisting fungus growth and of a sizeto pass a 10 mesh screen in an amount between 20% to 50% of the totaldry weight of the composition, exclusive of the binder, and theremainder comprising finely pulped cellulosic fibrous material in theform of individual fibers of an average length less than about 0.08inch; said particles and fibers being in substantially uniformvolumetric distribution, with said fibers. arranged in substantially alldirections, and said particles and presenting a continuous bonded fibersand binder structure that is microcellular, and comprises a multiplicityof substantially uniformly distributed substantlallymicrosqopic voids,said composition having a density in the order of about 7 to 9 poundsper cubic .foot dry weight and a thermal conductivity in the orderofapproximately 0.24 B. t. u./l 1r./sq. ft./inch thickness.

proofing agent.

amount toovercome such tendencies, said inhibiting agent comprising afungus growth in- .hibiting regranulated baked cork and the aqueousdistillate of natural cork boiling above 96 C.

'7. A fungus growth resistant composition adapted for insulationcomprising an organic material normally having fungus growth supportingtendencies and an inhibiting agent to overcome such tendencies and inamount greater than 30% by weight of the composition, said inhibitingagent comprising regranulated baked cork having the property ofresisting fungus growth of lessthan 6 pounds per cubic foot density andhaving less than 45% decomposition.

8. A light weight bonded composition adapted for insulation comprisingat least 30% finely divided regranulated baked cork having the propertyof resisting fungus growth bonded together with finely divided fibrousmaterial and a binder.

9. A fungus-resisting composition comprising fiber and 'regranulatedbaked cork.

10. A fungus-resisting composition comprising cellulosic fiber andhaving a density under 5 pounds per cubic foot.

11. A light weight compressed self-sustaining, uniformly microcellularfungus-resisting thermal insulating composition comprising principallyregranulated baked particles of finely divided cor having the propertyof resisting fungus growth, and finely pulped fibrous material comrandomorientation of said fibers imparting to said composition a uniformstructure substantially free from the layers of cleavage and parallelmatting of fiber characteristic of cardboard.

12. A compressed composition as cl claim 11, including to 6% ofdispersedwatercnAams -n.scnorr.

regranulated baked cork'r aimed .m

